Context Effects in Forensic Entomology and Use of Sequential Unmasking in Casework

Context effects are pervasive in forensic science, and are being recognized by a growing number of disciplines as a threat to objectivity. Cognitive processes can be affected by extraneous context information, and many proactive scientists are therefore introducing context‐minimizing systems into their laboratories. Forensic entomologists are also subject to context effects, both in the processes they undertake (e.g., evidence collection) and decisions they make (e.g., whether an invertebrate taxon is found in a certain geographic area). We stratify the risk of bias into low, medium, and high for the decisions and processes undertaken by forensic entomologists, and propose that knowledge of the time the deceased was last seen alive is the most potentially biasing piece of information for forensic entomologists. Sequential unmasking is identified as the best system for minimizing context information, illustrated with the results of a casework trial (n = 19) using this approach in Victoria, Australia.     

Assessing Cognitive Bias in Forensic Decisions: A Review and Outlook

In recent years, a number of studies have demonstrated that forensic examiners can be biased by task-irrelevant contextual information. However, concerns relating to methodological flaws and ecological validity attenuate how much the current body of knowledge can be applied to real-life operational settings. The current review takes a narrative approach to synthesizing the literature across forensic science. Further, the review considers three main issues: (i) primary research on contextual bias within forensic science; (ii) methodological criticisms of this research; (iii) an alternative perspective that task-irrelevant contextual information does not always lead to error. One suggestion for future research is outlined, which is that studies on contextual bias in forensic decisions should be conducted in collaboration between forensic scientists and cognitive psychologists. Only then can rigorous and ecological valid experiments be created that will be able to assess how task-irrelevant contextual information influences forensic analysis and judgments in operationally valid settings.     

Diagnosing Crime and Diagnosing Disease: Bias Reduction Strategies in the Forensic and Clinical Sciences

Cognitive effort is an essential part of both forensic and clinical decision‐making. Errors occur in both fields because the cognitive process is complex and prone to bias. We performed a selective review of full‐text English language literature on cognitive bias leading to diagnostic and forensic errors. Earlier work (1970–2000) concentrated on classifying and raising bias awareness. Recently (2000–2016), the emphasis has shifted toward strategies for “debiasing.” While the forensic sciences have focused on the control of misleading contextual cues, clinical debiasing efforts have relied on checklists and hypothetical scenarios. No single generally applicable and effective bias reduction strategy has emerged so far. Generalized attempts at bias elimination have not been particularly successful. It is time to shift focus to the study of errors within specific domains, and how to best communicate uncertainty in order to improve decision making on the part of both the expert and the trier‐of‐fact.     

Testing for Potential Contextual Bias Effects During the Verification Stage of the ACE‐V Methodology when Conducting Fingerprint Comparisons*

Abstract: This study was conducted to assess if fingerprint specialists could be influenced by extraneous contextual information during a verification process. Participants were separated into three groups: a control group (no contextual information was given), a low bias group (minimal contextual information was given in the form of a report prompting conclusions), and a high bias group (an internationally recognized fingerprint expert provided conclusions and case information to deceive this group into believing that it was his case and conclusions). A similar experiment was later conducted with laypersons. The results showed that fingerprint experts were influenced by contextual information during fingerprint comparisons, but not towards making errors. Instead, fingerprint experts under the biasing conditions provided significantly fewer definitive and erroneous conclusions than the control group. In contrast, the novice participants were more influenced by the bias conditions and did tend to make incorrect judgments, especially when prompted towards an incorrect response by the bias prompt.     

The Forensic Confirmation Bias: A Comparison Between Experts and Novices

A large body of research has described the influence of context information on forensic decision‐making. In this study, we examined the effect of context information on the search for and selection of traces by students (N = 36) and crime scene investigators (N = 58). Participants investigated an ambiguous mock crime scene and received prior information indicating suicide, a violent death or no information. Participants described their impression of the scene and wrote down which traces they wanted to secure. Results showed that context information impacted first impression of the scene and crime scene behavior, namely number of traces secured. Participants in the murder condition secured most traces. Furthermore, the students secured more crime‐related traces. Students were more confident in their first impression. This study does not indicate that experts outperform novices. We therefore argue for proper training on cognitive processes as an integral part of all forensic education.     

Identifying and measuring juror pre-trial bias for forensic evidence: development and validation of the Forensic Evidence Evaluation Bias Scale

Abstract

Previous research has provided support for the impact of juror pre-trial bias on judicial decision making, particularly in cases where the evidence presented at trial is of weak or ambiguous probative value. In an effort to identify whether a pre-trial bias for forensic evidence exists, the Forensic Evidence Evaluation Bias Scale (FEEBS) was developed and tested. The results of a principal components analysis suggested that two distinct constructs were being measured, corresponding to a pro-prosecution and pro-defence bias toward forensic evidence. In a second validation study, scores on these two subscales were compared with other existing juror bias measures (Juror Bias Scale and Belief in a Just World) and in a mock juror decision making task only the pro-prosecution subscale of the FEEBS predicted the perceived strength of forensic evidence. A partial mediation model is presented which explains the relationship between this bias and verdict preferences. The implications of this potential juror bias are discussed in the context of real juries, the CSI Effect (which refers to anecdotal claims that jurors are biased by the popularity of fictional representations of forensic science on television) and peremptory challenges, as well as future research directions.     

How Cross‐Examination on Subjectivity and Bias Affects Jurors’ Evaluations of Forensic Science Evidence

Contextual bias has been widely discussed as a possible problem in forensic science. The trial simulation experiment reported here examined reactions of jurors at a county courthouse to cross‐examination and arguments about contextual bias in a hypothetical case. We varied whether the key prosecution witness (a forensic odontologist) was cross‐examined about the subjectivity of his interpretations and about his exposure to potentially biasing task‐irrelevant information. Jurors found the expert less credible and were less likely to convict when the expert admitted that his interpretation rested on subjective judgment, and when he admitted having been exposed to potentially biasing task‐irrelevant contextual information (relative to when these issues were not raised by the lawyers). The findings suggest, however, that forensic scientists can immunize themselves against such challenges and maximize the weight jurors give their evidence by adopting context management procedures that blind them to task‐irrelevant information.     

Exploring the Impacts of Ordinary Laboratory Alterations During Forensic DNA Processing on Peak Height Variation,Thresholds, and Probability of Dropout,

Impacts of validation design on DNA signal were explored, and the level of variation introduced by injection, capillary changes, amplification, and kit lot was surveyed by examining a set of replicate samples ranging in mass from 0.25 to 0.008 ng. The variations in peak height, heterozygous balance, dropout probabilities, and baseline noise were compared using common statistical techniques. Data indicate that amplification is the source of the majority of the variation observed in the peak heights, followed by capillary lots. The use of different amplification kit lots did not introduce variability into the peak heights, heterozygous balance, dropout, or baseline. Thus, if data from case samples run over a significant time period are not available during validation, the validation must be designed to, at a minimum, include the amplification of multiple samples of varying quantity, with known genotype, amplified and run over an extended period of time using multiple pipettes and capillaries.     

Effect of History and Context on Forensic Pathologist Interpretation of Photographs of Patterned Injury of the Skin

In a previous study, a survey‐based analysis of pathologist diagnoses of patterned injury was performed. Subjects were provided with photographs of “classic” injuries and asked to diagnose the lesion in the absence of history or context. There was a relatively low diagnostic consensus among respondents. A second survey suggested that the disparate answers were not due to a strong belief in different diagnoses, but instead reflected how the respondents dealt with ambiguity. A third survey was created that asked participants to evaluate patterned injuries of the skin, but provided history and contextual information. The addition of history and contextual information increased consensus from a median of 80% to 98% on a per‐question basis. Confidence increased from a median of 56%–92%. These results demonstrate the importance of history and context in medical diagnosis of patterned injuries of the skin.     

The Status of Forensic Anthropology in Europe and South Africa: Results of the 2016 FASE Questionnaire on Forensic Anthropology

One of the goals of the Forensic Anthropology Society of Europe (FASE) is to map the existing education and practice opportunities in the field of forensic anthropology in order to support the development of the discipline and to optimize the training courses provided by the Society. To address this goal, an online questionnaire was sent to European and South African practitioners of forensic anthropology and related disciplines in 2016. The results of the questionnaire showed that the status and roles of forensic anthropologists vary depending on the national legal systems, education, and employment status of the practitioners. Despite the fact that the expertise of forensic anthropologists has been increasingly requested in a variety of investigations and the spectrum of tasks has become broader, including identification of living persons, specialized education in forensic anthropology is still restricted to a few graduate and postgraduate programs in European countries and to annual FASE courses.     

ISO Standards Addressing Issues of Bias and Impartiality in Forensic Work

The ISO/IEC 17020 and 17025 standards both include requirements for impartiality and the freedom from bias. Meeting these requirements for implicit cognitive bias is not a simple matter. In this article, we address these international standards, specifically focusing on evaluating and mitigating the risk to impartiality, and quality assurance checks, so as to meet accreditation program requirements. We cover their meaning to management as well as to practitioners, addressing how these issues of impartiality and bias relate to forensic work, and how one can effectively evaluate and mitigate those risks. We then elaborate on specific quality assurance policies and checks and identify when corrective action may be appropriate. These measures will not only serve to meet ISO/IEC 17020 and 17025 requirements, but also enhance forensic work and decision-making.     

Root Morphology and Anatomical Patterns in Forensic Dental Identification: A Comparison of Computer‐Aided Identification with Traditional Forensic Dental Identification*

Abstract: An online forensic dental identification exercise was conducted involving 24 antemortem–postmortem (AM–PM) dental radiograph pairs from actual forensic identification cases. Images had been digitally cropped to remove coronal tooth structure and dental restorations. Volunteer forensic odontologists were passively recruited to compare the AM–PM dental radiographs online and conclude identification status using the guidelines for identification from the American Board of Forensic Odontology. The mean accuracy rate for identification was 86.0% (standard deviation 9.2%). The same radiograph pairs were compared using a digital imaging software algorithm, which generated a normalized coefficient of similarity for each pair. Twenty of the radiograph pairs generated a mean accuracy of 85.0%. Four of the pairs could not be used to generate a coefficient of similarity. Receiver operator curve and area under the curve statistical analysis confirmed good discrimination abilities of both methods (online exercise = 0.978; UT‐ID index = 0.923) and Spearman’s rank correlation coefficient analysis (0.683) indicated good correlation between the results of both methods. Computer‐aided dental identification allows for an objective comparison of AM–PM radiographs and can be a useful tool to support a forensic dental identification conclusion.     

Reasons for Lack of Consensus in Forensic Pathologist Interpretation of Photographs of Patterns of Injury of the Skin,

In a previous study, a survey‐based analysis of pathologist diagnoses of patterned injury in which participants were asked makes diagnoses from photographs in the absence of history or context. The level of consensus was low. A follow‐up survey was created to ask those who responded to the first survey why they answered as they did or why they were unsure of their answers. The most common reason for lack of consensus was that the lesion was nonspecific. Responses invoking ambiguity were more common than those that indicated a confident difference in diagnosis. There were differences between demographic groups, with age and experience being most prominent. These findings suggest that differences in image interpretation do not generally reflect firm differences in diagnosis as much as differing ways of dealing with ambiguity in the absence of history and context. A third survey will study the effect of the addition of contextual information.     

刑事鉴定制度修改的背景、争议及解读

《刑事诉讼法》在鉴定问题上进行了大幅度地修改,改变了鉴定作为证据种类的名称,删除了"省级人民政府指定的医院"的规定,增加了对鉴定人出庭作证及其人身权利保障等内容,其进步意义应当是肯定的。然而,《刑事诉讼法》有关鉴定修改触及的内容均需要从修改的缘故、争议问题被修改的程度以及执行中可能遇到的障碍等方面予以理论分析与诠释,以便对此问题有一个科学的认识与理解。     

Validation of the New Interpretation of Gerasimov's Nasal Projection Method for Forensic Facial Approximation Using CT Data,

The most common method to predict nasal projection for forensic facial approximation is Gerasimov's two‐tangent method. Ullrich H, Stephan CN (J Forensic Sci, 2011; 56: 470) argued that the method has not being properly implemented and a revised interpretation was proposed. The aim of this study was to compare the accuracy of both versions using a sample of 66 postmortem cranial CT data. The true nasal tip was defined using pronasale and nasal spine line, as it was not originally specified by Gerasimov. The original guidelines were found to be highly inaccurate with the position of the nasal tip being overestimated by c. 2 cm. Despite the revised interpretation consistently resulting in smaller distance from true nasal tip, the method was not statistically accurate (p > 0.05) in positioning the tip of the nose (absolute distance >5 mm). These results support that Gerasimov's method was not properly performed, and Ullrich H, Stephan CN (J Forensic Sci, 2011; 56: 470) interpretation should be used instead.     

A Grass Molecular Identification System for Forensic Botany: A Critical Evaluation of the Strengths and Limitations*

Abstract: Plant material is frequently encountered in criminal investigations but often overlooked as potential evidence. We designed a DNA‐based molecular identification system for 100 Australian grasses that consisted of a series of polymerase chain reaction assays that enabled the progressive identification of grasses to different taxonomic levels. The identification system was based on DNA sequence variation at four chloroplast and two mitochondrial loci. Seventeen informative indels and 68 single‐nucleotide polymorphisms were utilized as molecular markers for subfamily to species‐level identification. To identify an unknown sample to subfamily level required a minimum of four markers or nine markers for species identification. The accuracy of the system was confirmed by blind tests. We have demonstrated “proof of concept” of a molecular identification system for trace botanical samples. Our evaluation suggests that the adoption of a system that combines this approach with DNA sequencing could assist the morphological identification of grasses found as forensic evidence.     

Arthropods of Forensic Importance on Pig Carrion in the Coahuilan Semidesert,Mexico

Abstract: This is the first report of an ongoing research to establish a sarcosaprophagous arthropod database in the Coahuilan semidesert. Seven pigs (Sus scrofa L.) were used as human models to determine succession in an open urban area during the 2007 winter–spring period. Arthropods were collected manually and from pitfall traps. Carcass biomass loss, as well as arthropod colonization, was recorded during 71 days postmortem. Five decomposition stages were identified during which most abundant orders were found to be Diptera, Coleoptera, and Hymenoptera. Lucilia sericata (Meigen), Chrysomya rufifacies (Macquart), Necrobia rufipes (DeGeer), Dermestes maculatus (DeGeer), Pheidole hyatti Emery, and Pogonomyrmex rugosus Emery stood out as dominant species.     

Strengths,Limitations, and Recommendations for Instrumental Color Measurement in Forensic Soil Characterization

Color determination of soil evidence is often done by visual comparison to soil color charts. A handheld spectrophotometer was tested with representative materials for its suitability for forensic soil characterization. Instrumental colorimetry provides accurate colorimetry with ~10-fold better precision than a soil color chart. The minimum sample size for accurate color determination was between 0.02 and 0.04 mg of fine soil for the specific instrument tested. Reporting colors in the L*a*b* space permits quantification of ΔE₀₀, a measure of perceptible color difference, could enable objective quantification of small color differences and thresholds for forensic soil comparisons. A ΔE₀₀ greater than ~ 3.5 to 6 likely indicates disparate soil sources in a forensic comparison, in the absence of confounding factors like sample alteration. Despite the superior precision of instrumental colorimetry, this approach is inappropriate for samples which are mottled at an inseparable scale, attached to a substrate, or too small for instrumental measurement.